/Engine/Source/Editor/UMGEditor/Public/WidgetBlueprintEditorUtils.h
static [TOptional](API\Runtime\Core\IO\TOptional)< [FWidgetThumbnailProperties](API\Editor\UMGEditor\FWidgetBlueprintEditorUtils\FWidgetThumbnailProperties) > DrawSWidgetInRenderTargetForThumbnail ( [UUserWidget](API\Runtime\UMG\Blueprint\UUserWidget) * WidgetInstance, [FRenderTarget](API\Runtime\Engine\FRenderTarget) * RenderTarget2D, FVector2D ThumbnailSize, [TOptional](API\Runtime\Core\IO\TOptional)< FVector2D > ThumbnailCustomSize, EThumbnailPreviewSizeMode ThumbnailSizeMode )